The present invention relates to the field of optical sensors and more particularly concerns a more efficient sensor for determining the position and orientation of a target object.
Optical sensors are useful tools for position and orientation measurements of objects of various types and sizes.
In particular, in the automobile industry where an automobile body must be inspected for defects during the manufacturing process, such sensors are used to collect measurements of the position and orientation of selected objects on the car body. The resulting data is stored in a database for analysis. This type of inspection is carried out using an articulated robot with a laser-camera mounted on its wrist, the laser-camera providing the measurements. The robot is moved over the car body and the camera takes measurements of selected objects. The robot can move in any direction and orientation over a selected feature of the car body. However, in order to measure position and orientation, the robot has to go to the selected feature area and rotate, tilt and turn the camera in several directions in order to capture all the measurements needed for the database. Even with these robot movements, the camera will not be able to measure all the angles needed for a proper characterization of the object.
The above explained inspection process has two important drawbacks. Firstly, for a given cycle, the inspection time is lengthen by the many movements of the camera necessary in order to capture the angles needed to provide the required data. Secondly, in order to take orientation measurements, the camera must be moved in several angles. These movements are sometimes impossible because other objects can be in the way of the robot and camera. The geometry of the car body becomes a limiting factor.
There is therefore a need for an optical sensor providing the data necessary for describing the position and orientation of an object without moving the camera around during the measurement process and without knowing the orientation of the camera and the robot wrist, which is not the case of prior art devices.
In accordance with a first aspect of the present invention, there is provided a sensing head for providing bi-dimensional and tri-dimensional data determinative of a position and an orientation of a target object extending in a sensing area.
The sensing head includes a general illumination light source directed towards the sensing area, and a bi-dimensional sensor also directed towards said sensing area. The bi-dimensional sensor cooperates with the general illumination light source for acquiring the bi-dimensional data upon illumination of the target object by the general illumination light source. The bi-dimensional data is representative of an image of the target object along a plane.
The sensing head also has a laser light source, and an optical arrangement optically coupled to the laser light source for controllable projection of a light output generated by the laser light source along distinct lines extending in the plane. A tri-dimensional sensor is directed towards the sensing area for acquiring the tri-dimensional data, by sensing diffusion of the light output on the target object. The tri-dimensional data is representative of tri-dimensional coordinates of the target object along the above-mentioned lines.
A collector circuit is connected to the bi-dimensional and tri-dimensional sensors for receiving the bi-dimensional and tri-dimensional data therefrom, the collector circuit having an output for transmitting the same.
In accordance with another aspect of the present invention, there is also provided an apparatus for determining a position and an orientation of a target object extending in a sensing area.
The apparatus includes a sensing head for providing bi-dimensional and tri-dimensional data determinative of the position and orientation of the target object. The sensing head has a general illumination light source directed towards the sensing area, and a bi-dimensional sensor, also directed towards the sensing area and cooperating with the general illumination light source for acquiring the bi-dimensional data upon illumination of the target object by the general illumination light source. The bi-dimensional data is representative of an image of the target object along a plane. The sensing head further includes a laser light source and an optical arrangement optically coupled thereto for controllable projection of a light output generated by the laser light source along distinct lines extending in the plane. A tri-dimensional sensor is directed towards the sensing area for acquiring the tri-dimensional data by sensing diffusion of the light output on the target object. The tri-dimensional data is representative of tri-dimensional coordinates of the target object along the lines. The sensing head also includes a collector circuit connected to the bi-dimensional and tri-dimensional sensors for receiving the bi-dimensional and tri-dimensional data therefrom. The collector circuit has an output for transmitting the same.
The apparatus further includes a control circuit for controlling the light sources and the sensors, and a processing circuit for processing the bi-dimensional and tri-dimensional data received from the collector circuit to determine therefrom the position and orientation of the target object.
Further advantages and features of the present invention will be better understood upon reading of preferred embodiments thereof with reference to the appended drawings.